Compounds of the following formula 2, which are 2,2′-binaphthol-3-aldehyde, can be very usefully used to separate chiral amino alcohols or amino acids into their respective optical isomers by recognizing their chirality through an imine bond or to convert L-amino acid into D-amino acid or D-amino acid into L-amino acid (see Korean Patent No. 10-0661280; H. Park, K. M. Kim, A. Lee, S. Ham, W. Nam, J. Chin, J. Am. Chem. Soc. 2007, 129, 1518-1519; K. M. Kim, H. Park, H. Kim, J. Chin, W. Nam, Org. Lett. 2005, 7, 3525-3527).

The respective compounds of the formula 2 can be prepared from the enantiomerically pure compounds of the following formula 1 by sequential alkylation of the 2 hydroxyl group, reduction, and oxidation thereof. Since the compounds of the formula 1 can be selectively alkylated at the 2 hydroxyl group, they are useful intermediates that can be alkylated in a high yield without using a protecting group. Thus, it is significantly important to prepare enantiomerically pure compounds 1a and 1b from racemic compound 1 of the formula 1 in an economical way.

A method of reacting racemic compound 1 of the formula 1 (2,2′-dihydroxy-1,1′-binaphthyl-3-carboxylic acid) with cinchonidine or cinchonine, and filtering and separating the obtained salts using the difference in the solubility of the salts has already been disclosed by Hovorka, M., et al. (Hovorka, M.; Stibor, I; Holakovsky, R.; Smiskova, I.; Struzka, V. Czech Rep. (2001), CZ 287879 B6). However, said method is uneconomical because cinchonidine and cinchonine used in the optical resolution are very expensive. Further, said method requires a large amount of solvents because of bad solubility of the obtained salts, which results in increase in reaction volume and a decrease in productivity. Due to these disadvantages, said method is not suitable for mass production.